Researchers Improve Science of Predicting
Catastrophes

Agricultural Research
Service scientists in New Mexico and cooperators have joined forces to
improve the science of predicting catastrophes, ranging from forest fires to
desertification and global warming.

By pooling their research, the scientists have constructed a
theoretical mathematical framework supported by data as a first step toward
developing the tools--including computer modelsand designing the
experiments needed to forecast and avert catastrophes that can begin with a
single tree or shrub, person or event.

Peters, an ecologist at the ARS
Jornada
Experimental Range near Las Cruces, N.M., began the inquiry by wondering
about similar dynamics between desertification and wildfires. She and
Bestelmeyer, also an ecologist, and research leader Kris Havstadboth at
the Jornadaand cooperators now theorize that there are common elements
between catastrophes that involve propagating eventslike disease
epidemics. Such events occur in four stages, with thresholds between each one.
At each stage, both the pace of events and the dominating processes or forces
change. When events cross the threshold after the third stage, they can become
irreversible.

For example, in the first stage of desertification, a shrub
invades a grass patch, creating bare spaces by taking water from grasses. The
shrub later drops seeds and spreads, crossing a threshold into stage two.

While overgrazing by cattle can push land over the threshold
from stage two to three, larger forcesoften weather, such as wind and
droughtbecome the dominant drivers after stage three.

This framework helps researchers and decision makers avoid
surprises by taking into account different dominant processes and dynamics
between stages.